The present invention relates to an automatic data logging kit that is composed of data logging equipment, pressure sensors, and temperature sensors along with mechanical hardware that is used with hydraulic integrity test (HIT) skids for testing liquid cooled stator bar systems found within power generators. The kit provides automatic data logging capabilities for the pressure-decay and vacuum-decay cycle tasks, increased accuracy of the pressure-decay and vacuum-decay data, and reduced cycle time. Computer logic calculates leak rates for each of these tasks. Additionally, the equipment can be used to determine and/or accommodate leaks in the test equipment.
Large dynamoelectric equipment, such as generators, typically use branched fluid cooling systems. Parts of this equipment, such as the stator coils, are internally cooled by the circulation of a liquid. Generally, the operational atmosphere of these parts is pressurized hydrogen. The pressure of the coolant in the coil is less, by design, than the pressure of the hydrogen ambient pressure. Theoretically, a leak in a coil carrying coolant should allow the entry of hydrogen to the coil rather than venting of fluid to the atmosphere. Unfortunately, a bubble of such hydrogen gas within the coil is sufficient to at least partially block the passage of the fluid coolant, thus creating hot spots that deteriorate stator insulation, diminish conductivity and ultimately cause shutdown of the equipment.
Periodic tests of conductivity of the stators are useful in prevention of accidents and unscheduled shutdowns of the equipment. The result of such tests depend, to some extent, on the degree to which all fluids and contaminants are first removed from the cooling lines. Periodic test protocols are also useful for determining advanced warning of breakdowns in the integrity of the lines, however minute. A hydraulic integrity test skid for performing these tests on dynamoelectric equipment is disclosed in U.S. Pat. No. 5,287,726.
One of the tests performed with the use of the HIT skids is a pressure-decay test, which measures the drop in pressure over time for a potentially leaking liquid cooled stator bar system in a generator. Current methods for running the pressure-decay test cycle are to perform the test over a twenty-four hour period and manually record readings once every hour. Inaccuracies can occur, however, with a sampling rate of one reading per hour and by the manual recording of data points including internal pressure, atmospheric pressure and multiple temperature readings. Still further, inaccurate volume measurements accounting for the HIT skid internal plumbing, pressure tanks, valves and interconnecting plumbing between the HIT skid and generator pervade data input for calculations in the pressure-decay cycle, adding a level of inaccuracy into the results. In addition, inaccurate temperature measurements can undermine the test due to the dependence on temperature by internal pressure. Additionally, the twenty-four hour period for the test can be significantly reduced to shorten overall outage time.
Another test performed with the use of the HIT skids is a vacuum-decay test, which measures an increase in pressure over time for a potentially leaking liquid-cooled stator bar system after being placed in a vacuum or reduced pressure state. Problems similar to those in the pressure-decay test, however, also occur with conventional vacuum-decay testing methods.
In an exemplary embodiment of the invention, an automatic data logging kit is provided for use with a hydraulic integrity test skid for testing a liquid cooled stator bar system. The automatic data logging kit includes a spool piece having end connectors attachable between the liquid cooled stator bar system and the hydraulic integrity test skid and a plurality of sensor receptacles. At least one temperature sensor is insertable within an interior of the liquid cooled stator bar system and includes an output connector operatively securable in a first of the sensor receptacles. At least one pressure sensor is operatively securable in a second of the sensor receptacles. A control unit receives output from the sensors and calculates a leak rate based on the received sensor output.
In another exemplary embodiment of the invention, the automatic data logging kit includes a spool piece with end connectors attachable between the liquid cooled stator bar system and the hydraulic integrity test skid. An elongated temperature probe is insertable within an interior of the liquid cooled stator bar system and has an output connector operatively securable in a first of the sensor receptacles. With the pressure sensor secured in a second of the sensor receptacles, a control unit receives output from the sensors and calculates a leak rate based on the received sensor output.
In yet another exemplary embodiment of the invention, a method of automatically logging data for testing a generator cooling system includes the steps of (a) logging data concerning temperature and pressure within the generator cooling system, the data being received from sensor outputs operatively coupled with the generator cooling system; and (b) automatically calculating a leak rate based on the logged data.